US1931948A - Boiler with reheater - Google Patents

Description

Filed July 25, 1950 1NVENTOR W61 bu'r H.Arm.coat 4/ M ATTQRNH Patented Oct. 24, 1933 uNirsofsrArss My invention .relatesto poweraplants' and to methods of operating the same, and more particularly to steam generating plants having steam reheaters, and aims to provide a commercial apparatus and method for steam utilization adapted to improve the heat efiiciency and length of life of a steam consuming prime mover.

In a steam turbine installationpf 55,000,k .w.I

capacity using a steam pressure of 120'0, lbs. su-

- Derheated steam is used on the high pressure turbine and the steam then reheated at 400,1bs. pressure, for the low pressure condensing turbine.

be generated in the high pressure turbine, and 42,500 k.w. will be generated in thelow pressure I. turbine, or 22 and 72 /2 respectively ofthe total power generated. It will ,be seen that a more ,uniform superheat delivered from the a steam reheater is more important. from an emciency standpoint that-a uniform superheat be delivered'from the primary superheater, as the II I I I I I I tube bank 16 of the boiler pass over the primary greater percentage of power the reheated steam. I

- Howeventhe ordinary plant having'a reheater is generated from is so arranged that the gases of combustion give I up heat to the water-walls in the furnace, to the boiler tubes and to the primary superheater be,- fore they do to the reheater. In the above mentioned' arrangement of boiler and auxiliary equipment,;it will be notedthat thesteam re heater works under a ccnsiderably'lower temperature than the primary superheater; due tov being. located farther away from the furnace and in a lowgas temperature zone. The superheat from the steamreheater over a range of ratings therefore has the characteristicof a convection superheater; that is, the superheatv falls oiif rapidly with a falling off of the-capacity of the. generating unit, whereas the superheat from the primary superheater does not fall off so rapidly, due to its being located in azone of .highergas temperature and at the same time absorbing some heat by radiation; This order of. arrangement of primary superheater and gas reheater has been.

used heretofore on accountof giving greater protection to the steam reheater in'the startingup and shutting down p'eriods'but involves the disadvantages above noted;

'0 d steam generating and reheating arrangement and a method of operating-thesame wherebyv the steam from the reheater. is kept at an' approxi- ,mately uniform temperature with varying loads on the prime mover associated therewith. An, advantage associated with this'object is'thatit is also relatively more important to'keep the: turbine at consant temperature throughout its: low temperature section than throughoutthe high temperature section for the reason that cutting of I Assuming average temperatures of superheat and reheat, approximately 12 500 k,w-. .wil1 I I I draw n ,t

,, low pressure section 38 of turbine 32.

It is an objectof my inventionxto provide a the turbine blades by water in the steam-is most and to maintain a substantially constant steam temperature at the outlet of the reheater.

TheY novel features of my invention are pointed out with particularity inv the appended claims, but in order that the invention may be clearly understood I will now describe in detail, in connection with the accompanying drawing, an illustrative, embodiment of my invention.v In said Thef gure is a sectional elevation, somewhat diagrammatic in character, of a power plant in r 1 accordance with my invention.

Referring to the drawing more detail, the power plant therein illustrates aboile'rrljohavingwater cooled furnace chambers 12 and '14,

the gases from which, afterflowi'ng'through the generated the boiler -10 is taken from drum 28 through pipe 30 and, after passing through 'the superheater 18 goes through the high pressure section 31 of the turbine 32', I Steam leaving high pressure section 31 passes through a pipe 34 to a reheater 2Q and thence through pipe 36' to the I I I After passing through sectiont38 steam'passes to the condenser 40. v f' a In order that the steam for. the. low pressure stage ofturbine32lmay be delivered from reheater 26 at an approximately constant temperature, the reheater-'20 is' placed in 'a gas iluesepa rate from that containing the primary superheater l8. Inth'e' arrangemen't illustrated, thetubes in bank 16 are, inclinedsomewha't to'the horizontal but. extend above bothfthe furnace chambers 12 and 14. 'Ihe combustion gases from the two furnace'ifchambers, jhowever', v are pre-- vented from mixing'bywall 42' intermediatethe two chambers which runs vertically upward to the mid-point'of the tubes 16 and is then'ce'continuedlupward in the form of 'a. bafiie 44 which runs upf to the level of the top of .the'rehe'ater' -20'., The, furnace chamber .12, one' -half'fof the tubes of bank 16 and the. 'superheater T8 are therefore in one gas flue, and furnace chamber 14, the other halfof the tubes 16 andthereheater 2i) in.,another. I The flue 22 connects through the chamber46 above the upperjends of the superheate'r 18, reheater 20 and battle 44 so ,that the same 'stackmay be used for'both furnaces if desired,v However, the rate of combustion infurna'ce'ichambers 12 and 14 willnot be the same, fuel being burned in chamber 14 only outlet 48 of reheater 20. Furnace chamber 12,v

however, will be operated at such combustion rates as required to furnish steam for the varying loads on turbine 32. For supplying fuel to chambers 12 and 14 I have illustrated burners 50 and 52 respectively, with pulverized fuel, but I do not limit myself to any particular form of fuel feeding apparatus. It will be seen, however, that the reheater 20 is protected from excessive temperatures by the tubes in bank 16 which extend therebeneath. As, in general, the rate of combustion in chamber 12 is greater than that in chamber 14, or at least reaches higher maximum, I prefer to provide a greater amount of protection against high gas temperatures for the superheater 18 than for the reheater 20, and for this reason I provide beneath superheater 18, in addition to the tubes of bank 16 additional tubes 54 which extend above the furnace 12 but not over furnace 14.

y, In the arrangement illustrated, tubes 54 connect at their upper ends with the uptake header 56 of the boiler 10, and in order to supply water to the lower ends of tubes 54, I prefer to provide water headers 57, 5'7 in a masonry pier 58 on whichthe dividing wall 42 is supported and to extend water wall tubes 60, 60 upwardly from.

the headers 57 on each side of the wall 60 to connect with the generating tubes '54 at points 62, 62 adjacent the bank 16. It will be seen,"

therefore, that the tubes 60 not only act as risers for the boiler tubes 54 but also protect the wall 42 as well as increasing the efficiency of the chambers 12 and 14 by supplying radiant water wall surfaces therefore. Preferably the chambers 12 and 14 are provided with additional water wall tubes 64 and 66 respectively, which are con- ;nected to the boiler 10 at convenient points by any suitable means. I

The upper portion 44a of the baffle 44' which lies above the tube bank 16 and intermediate the steam heaters 18 and 20 is preferably supported independently of the tubes 16 and, for this purpose, I' prefer to employ a special set ,of generating tubes 68 which are shown as connecting at their lower ends with lower header 70 of the boiler 10 and thence running parallel to tubes 16 and above such tubes to the plane of the baffle 44 at which point tubes'68 bend sharply upward and run vertically between heaters 18 and 20 to a point near theroof of the boiler where they are supported by brackets 72 to a beam '74 and, are then bent horizontally and run to a'connection with the drum 28 at 76. The

section 4411 is attached to the tubes 68 so that the weight of such section is carried by beam 74 instead of falling on the bank 16. The tubes 68, lying below the reheater 20, add somewhat tothe generating surface between the reheater and furnace 14, but there need be only one 'row of tubes 68 and they may be spaced further apart than tubes .16 and 54 so that their presence does notmaterially offset the effect of the tubes 54 to equalize the generating surface. beneath the steam heaters 18 and 20.

It will be seen that the tubes of bank 16 all operate at high volumetric efficiency for the reason that there are no baflles extending transversely of the flow of the gases to form dead pockets or corners. It will be seen further that the reheater tubes are sufficiently protected from overheating and it will be understood that-the steam delivered of the type ordinarily employed said lower header."

from the superheater, while not having as uniform temperature as that delivered by the reheater, does not vary in temperature beyond the limit set by good commercial practice.

While I have described in detail a specific embodiment of my invention, I do not limit myself to the .detailsof the foregoing disclosure and I wish it to be understood in particular that my invention is of sufiicient scope in certain directions to include operating the reheater without water tubes between the reheater and the combustion chamber therefor.

What I claim is:

1. The combination of two separate furnaces, a bank of steam generating tubes spanning both said furnaces, means forming separate gas fines for said'furnaces extending through and above said bank, a superheater in one of said fiues above said bank, a reheater in' another of said flues above said bank, and means whereby the one of said flues having said superheater therein has alsoa greater extent of generating surface therein than the flue for said reheater 2. The combination as set forth in claim 1 together with two sets-of water wall tubes adjacent 100 each other and one exposed to radiation from one furnace'and the other to radiation from the other furnace, both said sets of water wall tubes extending beneath thesuperheater.

3. The combination with a boiler having a 105 steam and water drum, a horizontally inclined tube bank, upper and'lower headers for said bank and circulators'oonnecting said headers tosaid drum, of a bafiie within said bank and extending upwardly toa point above the same and means for supporting the portion of said baffle above said bankincluding water tubes secured to said portion and having their upper ends connected to said drum an'dtheirlower ends connected to 4. The combination as set forth in claim 3 together with a reheater on the side of the upper extension of the baffle and between it and the vertical plane including the lower header, and a superheater on the other side of the upward extension of the baffle.

5. The combination of two separate furnaces,

a bank of steam generating tubes spanning both said furnaces, means forming separate gas flues for said furnaces extending thru said bank and each flue carrying the entire gas flow from one furnace, a superheater in one of said dues and arranged to receive the steam formed in said bank and a fluid heater in the other of said fiues and having a heat demand independent of the rate of 3 the heat demand of said bank of tubes.

6. The combination as set forth in claim 5 and in which the superheater is in the gas flue having the greater extent-of generating surface therein.

'7. The combination of two separate furnaces, a bank of generating tubes spanning both of said furnaces, means for maintaining the gases from said furnaces separate thruout said bank, a superheater on one side of said separating means and arranged to receive the steam generated in said bank, a'fiuid heater on the opposite side of said operating means from said superheater and having a heat demand independent of the heat demand of said bank, two water walls between said furnaces composed of tubes having extensions lying beneath the portion of said bank on the

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